1. Field of the Invention
This invention relates to a projector, and more particularly, is applicable to a projector for projecting a color image.
2. Description of the Related Art
Heretofore, as a projector of this kind, there has been the projector employing a mirror deflection type light modulator (referred to as a mirror light valve hereinafter, Digital Micromirror Device, DMD) which comprises minute mirror elements arranged on a plane each corresponding to each pixel and utilizes the reflection of each mirror element.
In the projector, light based on the red, green and blue components of an image data is formed by respectively corresponding mirror light valves as an image source and the thus formed light based on the red, green and blue light components is projected enlargedly onto a screen to form a color image thereon based on the image data.
FIG. 1 shows an example of the projector employing three mirror light valves respectively corresponding to the red, green, and blue components of the image data.
In the projector 1, white light consisting of substantially parallel light emitted from a high luminance white light source 2 (referred to as projection light hereinafter) L1 passes through an ultra violet (UV) cut filter (not shown) to get rid of unnecessary ultra violet therefrom and through a condenser lens 3 to be converted into parallel light having a narrower beam diameter so as to be incident to decomposing dichroic mirrors 5R, 5G, and 5B by a first reflecting mirror 4.
The decomposing dichroic mirrors 5R, 5G, and 5B decompose in color the incident projection light L1 into red light LR, green light LG, and blue light LB. The red light LR, green light LG, and blue light LB pass through beam shaping cylindrical lenses 6R, 6G, and 6B to be subjected to beam shaping therein and are incident by way of second reflecting mirrors 7R, 7G, and 7B to the reflecting surfaces of mirror light valves 8R, 8G, and 8B in such a manner as to be homogeneous thereon in illumination distribution.
Each of the mirror light valves 8R, 8G, and 8B comprises a plurality of minute mirror elements respectively arranged in accordance with the arrangement of image data pixels. Each minute mirror element is arranged to correspond to each memory cell of a frame memory which cell corresponds in arrangement to each pixel of the image data, and is separately varied in inclination in accordance with the state of its corresponding memory cell so as to selectively reflect light incident thereto as effective reflected light necessary for forming an image or ineffective reflected light.
In the projector 1, image data for one frame respectively based on red, green, and blue components are set in frame memories corresponding to the mirror light valves 8R, 8G, and 8B respectively, and a driving circuit (not shown) drives under control the minute mirror elements based on the image data to form effective red light, effective green light, and effective blue light as effective reflected light. The effective red light, effective green light, and effective blue light are focused by their corresponding relay lenses 9R, 9G, and 9B respectively, and are directed to composing dichroic mirrors 10R, 10G, and 10B to be composed into color image light, which is enlargedly projected onto a screen (not shown) provided outside the projector 1 apart therefrom by way of a projector lens 11 having a zoom lens structure.
In this way, the projector 1 is capable of projecting a color image based on an image data.
Whereas the projector 1 having such a structure had a problem of becoming complicated in the optical system thereof and consequently large as a whole, since the projector 1 comprised an optical system for decomposing the projection light L1 emitted from the high luminance white light source 2 into the red light LR, green light LG, and blue light LB and an optical system for composing the effective red light, effective green light, and effective blue light respectively formed by the mirror light valves 8R, 8G, and 8B into color image light.
Thus the projector 1 had a problem that it used many optical components to be increased in cost.
The projector 1 had also a problem that it was troublesome to attach the optical components thereto or adjust the attached optical components since it used many optical components.